The purpose of this study is to evaluate serum osteocalcin and urine pyridinoline as potential screening markers for detecting early osteopenia in women who are amenorrheic. Serum osteocalcin and urine pyridinoline will be measured in both amenorrheic and eumenorrheic athletes. In addition, each athlete will undergo a dual-photon bone densitometer measurement of their bone mineral density which will serve as the gold-standard measurement of osteopenia.